Earthquake · reviewed by a seismologist
M 2.3md
Earthquake near Alamo, CA
No earthquake was likely felt in Alamo in the 24 hours to 3:17 am PST (11:17 UTC). The last one was M 2.1, 11 km (7 mi) NNW, at 4:05 am PST on 8 November 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Alamo
This page: a magnitude 2.3 earthquake was recorded 2 km (1 mi) south-southwest of Alamo, CA, at 6:54 am PDT on 25 April 2018 (13:54 UTC), 13 km deep.
USGS: 2km SSW of Alamo, CA
17 km (11 mi) ENE of Oakland, CA · 8 km (5 mi) S of Walnut Creek, CA
- When
- 6:54 am PDT on 25 April 2018 ()
- Where
- 2 km (1 mi) south-southwest of Alamo, CA · earthquakes near Alamo
- Magnitude
- M 2.3 (md)
- Depth
- 13 km below the surface
- Felt
- no reports yet
- Nearest
- Contra Costa County, 13 km NE
- Nearest mapped fault
- Calaveras fault, 2 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 3121 days ago
Earthquake alerts for Alamo, CA
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Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
At this magnitude and depth, people at rest would likely notice it out to about 15 km (9 mi) from the epicentre. In Alamo, 2 km away, the estimate is intensity II (weak). Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.
Likely felt in: Alamo 2 km, intensity II · Danville 4 km, intensity II · Walnut Creek 8 km, intensity II · San Ramon 8 km, intensity II · Lafayette 9 km, intensity II · Orinda 13 km, intensity II · Pleasant Hill 13 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 85 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.3 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 180,000× the energy of this one
- Magna, Utah 2020 M 5.7 130,000× the energy of this one
- Around the size people start to feel M 3.0 11× the energy of this one
- This earthquake M 2.3 about 85 lb of TNT
Energy from the Gutenberg–Richter relation (log10E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.
For this area
The largest earthquake within 50 km since 2016 was M 4.4 on 2018-01-04 — about 1,300 times the energy of this one.
Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:
- 7.9 The 1906 San Francisco, California Earthquake · 45 km WSW of this epicentre
- 6.0 The 2014 South Napa, California Earthquake · 48 km NNW of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 24 km E of this epicentre
- 5.4 9 km NE of Livermore, California · 31 km ESE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 43 km WSW of this epicentre
Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.
Where
Epicentre 37.8335, -122.0455. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 13 km (8 mi) | NE | earthquakes near Contra Costa County |
| Alameda County, CA | 24 km (15 mi) | SSE | earthquakes near Alameda County |
| Solano County, CA | 49 km (31 mi) | N | earthquakes near Solano County |
| San Mateo County, CA | 55 km (34 mi) | SSW | earthquakes near San Mateo County |
| Marin County, CA | 66 km (41 mi) | WNW | earthquakes near Marin County |
| San Joaquin County, CA | 69 km (43 mi) | E | earthquakes near San Joaquin County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
59 earthquakes have been recorded within 50 km since this one.
- 2.0 2km SW of Oakley, CA
- 2.7 2km SW of Oakley, CA
- 3.2 1km SW of Oakley, CA
- 1.7 1km SE of Oakley, CA
- 1.8 1km SE of Oakley, CA
- 2.3 3km N of Rodeo, CA
- 1.6 3km NE of Fremont, CA
- 2.5 2km ENE of Danville, CA
- 1.6 1km SW of Alamo, CA
- 1.6 2km NW of Diablo, CA
- 2.0 8km N of Pittsburg, CA
- 1.6 3km W of Concord, CA
- 1.7 2km E of Danville, CA
- 2.4 2km E of Danville, CA
- 1.7 2km ESE of Danville, CA
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.
On USGS
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.